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The slope method (Al-Zoubi, 2008, Geotech. Test. J., Vol. 31, No. 6, pp. 526–530) in which the coefficient of consolidation cvwas expressed as function of the EOP settlement δpand slope mof the initial linear portion of the observed δt− √tcurve is modified for improving the procedure used for estimating the EOP δp. The slope method EOP δpvalues were estimated using the point at which δt− √tcurve starts to deviate from the initial linear portion. In this note, the EOP δpis determined based on a unique relationship between the ratio of the secant slope of δt− √tcurve at 50 % consolidation to the secant slope at any time arbitrarily selected beyond the initial linear portion of the δt− √tcurve (theoretically, at U≥ 52.6%) and average degree of consolidation U. The modified slope method requires a minimum of four compression-time data points for better cvestimates. Two types of EOP settlement are identified; local EOP settlement δpiis obtained at a specific Uivalue as is the case in the Taylor method and global EOP settlement δpis determined independently of any Uvalue. The modified slope method yields δpand cvvalues quite similar to those of the Casagrande method.

The slope method explicitly relates the coefficient of consolidation cvto the slope of the initial linear segment of the observed δt-tcurve and to the end of primary settlement δp. The slope method utilizes the same graphical construction as the Taylor method but eliminates the use of the factor 1.15 that usually leads to lower δpand higher cvas compared to the Casagrande method and pore water pressure measurements. Instead, the point at which the δt-tcurve deviates from the linear portion (at Uof about 50 %) is considered for estimating δp. Oedometer test results on four soils show that the cvvalues of the slope and Casagrande methods are comparable but lower than those of the Taylor method.